1. Field of the Disclosure
The present application is generally directed to sapphire substrates and methods of finishing such substrates.
2. Description of the Related Art
Semiconducting components based on single crystal nitride materials of Group-III and Group-V elements are ideal for devices such as light-emitting diodes (LED), laser diodes (LD), displays, transistors and detectors. In particular, semiconductor elements utilizing Group-III and Group-V nitride compounds are useful for light emitting devices in the UV and blue/green wavelength regions. For example, gallium nitride (GaN) and related materials such as AlGaN, InGaN and combinations thereof, are the most common examples of nitride semiconductor materials in high demand.
However, manufacturing boules and substrates of such nitride semiconducting materials has proven difficult for a multitude of reasons. Accordingly, epitaxial growth of nitride semiconducting materials on foreign substrate materials is considered a viable alternative. Substrates including SiC (silicon carbide), Al2O3 (sapphire or corundum), and MgAl2O4 (spinel) are common foreign substrate materials.
Such foreign substrates have a different crystal lattice structure than nitride semiconducting materials, particularly GaN, and thus have a lattice mismatch. Despite such mismatch and attendant problems such as stresses and defectivity in the overlying semiconductor materials layer, the industry demands large surface area, high quality substrates, particularly sapphire substrates. However, challenges remain with the production of high quality substrates in larger sizes.